Patent GB-661098-A (GB)
Title: Method and apparatus for wet spinning artificial filaments
IPC: D01D5/06
Filed: 1948-05-12
Abstract: <PICT:0661098/IV (a)/1> <PICT:0661098/IV (a)/2> Artificial filaments are formed by the extrusion of a filament-forming material in a plurality of streams into a coagulating bath, directing the filaments through said bath a distance of not more than two inches and from the bath to a directional guide means outside the bath, and conducting substantially all of the liquid withdrawn by the filaments from the bath with the filaments and without back flow along the filaments to the directional guide means, said filaments, during their travel from the bath to the directional guide means, being subjected to substantially no greater tension than the weight of the filaments and the liquid bath carried by them.  Filaments of high combined quality index are obtained.  (The quality index is defined as the product of the extensibility and the tensile strength, and the quality indices obtained for the wet and dry filaments are added together.)  Spinning speeds may be from 40 to 160 or more metres per minute.  The immersion length in the bath is not more than 2 inches and preferably from 1 1/4 inches to 1/8 inch, the filaments emerging without turbulence and without apparent back flow of coagulating liquid.  The filaments pass from the spinneret to a positively driven draw-off means such as a godet, roller or thread storage device.  If desired, a directional guide means may lightly contact the filaments on the way from the bath to the draw-off means, or the directional guide means may be the draw-off means.  The filaments may be in contact with the draw-off means for less than 360 degrees of its periphery, or may be wrapped round in successive turns for storage and additional regeneration.  They may be positively stretched and/or treated in other liquid baths.  During the time of travel they are maintained substantially free from tension.  If desired the liquid withdrawn by the filaments is collected at the directional guide means and either reclaimed or run to waste. The load on each filament carrying liquid as a smooth column should not exceed 0.002 to 0.0025 gram per inch of length and is preferably within the range of 0.00025 to 0.0015 gram per inch of length.  The holes in the spinneret should be 0.005 to 0.015 inches apart, the same distance separating each circle of holes. The invention may be carried out with pot or bobbin spinning or with a continuous process.  As shown, the spinneret 2 is mounted in the bath 1 and the spinning solution extruded vertically, the filaments formed being drawn off by the rotating draw-off means 4. Between the draw-off means and the surface of the bath is a directional guide means 5 with which the filaments make light contact.  The guide means may be rotatable or fixed and is inclined to the horizontal so that any liquid removed from the filaments will be conducted out of the path of the filaments.  The filaments pass from the draw-off means to the godets 9, 10 where they are positively stretched.  Treatment in hot water, dilute acid or other setting-up treatment may be effected in a bath 8. The spinneret may be laterally spaced from the directional guide means if desired.  The directional guide means may be the draw-off means 24, if desired, as in Fig. 4. The distance H may be 6-30 inches and is preferably 12-18 inches. The liquid withdrawn from the bath by the filaments is thrown off the wheel by centrifugal force and collected in trough 17 from which it is led away by pipe 22 for reclamation or to waste.  The draw-off wheel may be slightly fluted in order to draw off the filaments upwardly.  The process is applicable to the spinning of viscose, cuprammonium, cellulose nitrate and other filaments where the solution is extruded into a liquid bath.